This invention relates to a magnetic disk apparatus, and more particularly relates to a technique that is effectively applied to a magnetic disk apparatus having a semiconductor chip on an arm of a carriage mechanism.
A magnetic disk apparatus, which is to be incorporated in a personal computer or an electronic system of a network system server, mainly comprises a disk-shaped magnetic recording medium that is rotated at high speed by a spindle motor (referred to as magnetic disk hereinafter), a magnetic head for writing (recording) the data in a magnetic disk and for reading out (reproducing) the data written in a magnetic disk, a carriage mechanism for moving the magnetic head to an arbitrary position on a magnetic disk, a semiconductor chip (referred to as read/write semiconductor chip hereinafter) in which an amplifier circuit for amplifying the analog signal read out by means of the magnetic head, an A/D circuit for converting the analog signal that has been amplified by means of the amplifier circuit to the digital signal, and a control circuit or the like for controlling various signal are incorporated, and these components are contained in a single housing.
The carriage mechanism comprises an actuator and an arm for transmitting the power of the actuator to the magnetic head. The arm comprises a root part (carriage portion) fixed to a rotation shaft that is rotated by means of the actuator, an arm body portion that is continuous to the root part of the arm, and a suspension portion that is continuous to the arm body portion that has the magnetic head. The suspension portion usually comprises a separate parts different from the arm body portion, and is attached to the arm body portion by means of a fixing means.
The magnetic head comprises a writing head for writing the data in a magnetic disk, a reading head for reading out the data written in a magnetic disk, and a slider for generating the floating force by means of air flow due to rotation of a magnetic disk. The magnetic disk floats with a small distance from the recording surface of a magnetic disk by means of floating force due to the slider and deflection of the suspension portion of the arm, and the data is written or read out in this floating state.
Usually, the front side and back side of a magnetic disk that are opposed to each other are used as the recording surface for recording the data, and a plurality of magnetic disks are piled up with interposition of a predetermined space, a plurality of arms and magnetic heads corresponding to the number of recording surfaces are used.
In such a magnetic disk apparatus, the wire wiring in which wire is fixed along an arm has been employed as the connection means for electrical connection between a magnetic head and a read/write semiconductor chip. However, in order to enhance the productivity and realize the high data transfer speed, recently electrical connection between the magnetic head and the read/write semiconductor chip, in which wiring member formed by thin film forming technique is formed on an arm is employed as a trial. This technique is described in, for example, Nikkei Electronics, issued on April 1998, 6, (No. 713), pp. 167-177, by Nikkei BP.
A method is employed as a trial, in which a semiconductor chip (referred to as amplifier semiconductor chip hereinafter) containing a built-in amplifier circuit for amplifying the analog signal read out by means of a magnetic head and a built-in A/D conversion circuit for converting the analog signal amplified by means of the amplifier circuit to the digital signal is located on the suspension part of the arm or body part of the arm and a semiconductor chip (referred to as control semiconductor chip hereinafter) containing a built-in control circuit for controlling various signals is located on the root part of the arm. Such technique is described in, for example, Japanese Published Unexamined Patent Application No. Hei 11(1999)-195202 (published Jul. 21, 1999).
In this method in the case that an amplifier semiconductor chip is located on the suspension part of the arm or located on the arm body part, a method is employed generally, in which the semiconductor chip is fixed on the chip fixing area of the wiring member so that the back surface opposed to the circuit forming surface of the semiconductor chip is facing to the wiring member, thereafter an electrode (bonding pad) formed on the circuit forming surface of the semiconductor chip is electrically connected to the wiring of the wiring member by use of a bonding wire, and resin is coated on the semiconductor chip and bonding wire for covering to protect the circuit forming surface of the semiconductor chip and the bonding wire (simply referred to as face up method hereinafter).
However, in the case of the face up method, because the thickness of the resin coated on the circuit forming surface of the semiconductor chip is inevitably thick correspondingly to the loop height (height from the circuit forming surface of the semiconductor chip to the top in the perpendicular direction) of the bonding wire, it is required to widen the space between magnetic disks, and such structure brings about the difficulty in designing the thin magnetic disk apparatus. Furthermore, because the signal transmission path between the electrode of the semiconductor chip and the wiring of the wiring member is inevitably long, such structure also brings about the difficulty in designing the high rate data transfer.
A method (simply referred to as face down method hereinafter) described hereinafter may be effectively employed in the case that an amplifier semiconductor chip is located on the suspension part of an arm or on the arm body part, in which an electrode of the semiconductor chip is electrically connected to a wiring of a wiring member with a projection electrode interpolated between the electrode of the semiconductor chip and the wiring of the wiring member and resin is filled between the semiconductor chip and the wiring member for covering the circuit forming surface of the semiconductor chip and the projection electrode to protect the circuit forming surface and the projection electrode. In the case of the face down method, the height of the projection electrode offsets the thickness of the resin, the space between magnetic disks can be narrower than that in the case of the face up method, and the thickness of the magnetic disk apparatus can be smaller. Furthermore, because the signal transmission path between the electrode of the semiconductor chip and the wiring of the wiring member is shorter in comparison with that in the case of the face up method, the higher data transfer rate can be realized.
However, the face down method is involved in a problem as described hereinafter. A semiconductor chip mainly comprises a semiconductor substrate formed of, for example, single crystal silicon. Such semiconductor chip is generally formed by means of a process in which a plurality of chip forming areas are formed on the circuit forming surface of a semiconductor wafer (semiconductor substrate) and the semiconductor wafer is diced, and the plurality of chip forming areas are divided into individual areas. Because a semiconductor substrate formed of single crystal silicon is hard and brittle, many small broken and cracks are formed on the edge portion of the circuit forming surface side (corner where the cut surface and the circuit forming surfaces intersect) and edge portion on the back side (corner where the cut surface and the back surface intersect) of the semiconductor chip divided by dicing. Because the broken and crack can cause fragments (silicon dust) separated from the semiconductor substrate, the semiconductor chip is apt to release debris.
In the case of the face down method, because the edge portion on the circuit forming surface side of the semiconductor chip is covered with resin filled between the semiconductor chip and the wiring member, the release of debris from the edge portion on the circuit forming surface side of the semiconductor chip is suppressed, however, because the back side of the semiconductor chip is exposed, debris is released from the edge portion on the back side of the semiconductor chip.
In the case that such debris remains on the recording surface of a magnetic disk, the debris is interposed between the recording surface of the magnetic disk and a magnetic head, the recording surface of the magnetic disk and the magnetic head are damaged or failure in writing of the data and reading out of the data is caused, and the reliability of the magnetic disk apparatus becomes seriously poor.
The failure due to debris of semiconductor chip is apt to arise in the case that a semiconductor chip is located on the suspension part of an arm and arm body part by means of the face down method. However also in the case of the face down method that a semiconductor chip is located on the root part of an arm and on the area other than the carriage mechanism, because a magnetic disk rotates at high speed in a closed housing and air flow due to rotation of the magnetic disk blows off debris on the area other than that of the magnetic disk and the debris falls down on the recording surface of the magnetic disk, the debris causes the failure.
Furthermore, recently, it is the trend that the areal recording density is increased to increase the recording capacity (number of bits recordable per one inch square). The increase in the areal recording density inevitably reduces the area of a magnetic pattern for one bit, and the magnetic force is weak and it becomes difficult to read out the data. To solve such problem, the floating distance between the recording surface of a magnetic disk and a magnetic head is reduced to read the weak magnetic force easily. Therefore, the suppression of the release of debris from a semiconductor chip is important for the magnetic disk apparatus.
It is an object of the present invention to provide a technique to improve the reliability of a magnetic disk apparatus.
The above-mentioned and other objects and features of the present invention will be apparent from the description of the present specification and with reference to the attached drawings.
The summary of the representative inventions will be described hereinafter out of inventions disclosed in the present patent application.
(1) A magnetic disk apparatus comprises;
a disk-shaped magnetic recording medium (magnetic disk) that rotates in operation,
a magnetic head for writing the data in the magnetic recording medium and for reading out the data written in the magnetic recording medium,
a carriage mechanism having an arm on which the magnetic head is located and moving the magnetic head to an arbitrary position on the magnetic recording medium,
a wiring member having wiring,
a semiconductor chip having a first main surface (circuit forming surface) and a second main surface (back surface) that are opposed to each other and electrodes formed on the first main surface, the semiconductor chip being fixed to the wiring member in the state that the electrodes are facing to the wiring of the wiring member, and
a housing that contains the magnetic recording medium, the magnetic head, the carriage mechanism, the wiring member, and the semiconductor chip,
wherein the edge of the first main surface side of the semiconductor chip and the edge of the second main surface side are covered with insulative resin.
(2) The side surface (dicing surface) of the semiconductor chip is covered with the resin in the magnetic disk apparatus described in the means (1).
(3) A magnetic disk apparatus comprises;
a disk-shaped magnetic recording medium that rotates in operation,
a magnetic head for writing the data in the magnetic recording medium and for reading out the data written in the magnetic recording medium,
a carriage mechanism having an arm on which the magnetic head is located and moving the magnetic head to an arbitrary position on the magnetic recording medium,
a wiring member having wiring,
a semiconductor chip having a first main surface and a second main surface that are opposed to each other and electrodes formed on the first main surface, the semiconductor chip being fixed to the wiring member in the state that the electrodes are facing to the wiring of the wiring member, and
a housing that contains the magnetic recording medium, the magnetic head, the carriage mechanism, the wiring member, and the semiconductor chip,
wherein;
the electrode of the semiconductor chip is electrically connected to the wiring of the wiring member with interposition of a projection electrode,
the edge of the first main surface side of the semiconductor chip is covered with resin filled between the first main surface of the semiconductor chip and the wiring member, and
the edge of the second main surface side of the semiconductor chip is covered with resin located so as to cover the second main surface of the semiconductor chip.
(4) A magnetic disk apparatus comprises;
a disk-shaped magnetic recording medium that rotates in operation,
a magnetic head for writing the data in the magnetic recording medium and for reading out the data written in the magnetic recording medium,
a carriage mechanism having an arm on which the magnetic head is located and moving the magnetic head to an arbitrary position on the magnetic recording medium,
a wiring member having wiring,
a semiconductor chip having a first main surface and a second main surface that are opposed to each other and electrodes formed on the first main surface, the semiconductor chip being fixed to the wiring member in the state that the electrodes are facing to the wiring of the wiring member, and
a housing that contains the magnetic recording medium, the magnetic head, the carriage mechanism, the wiring member, and the semiconductor chip,
wherein;
the semiconductor chip is adhered and fixed to the wiring member with interposition of anisotropically conductive resin containing much conductive particles mixed in insulative resin base material,
the electrode of the semiconductor chip is electrically connected to the wiring of the wiring member with interposition of a projection electrode and conductive particles contained in the anisotropically conductive resin,
the edge of the first main surface side of the semiconductor chip is covered with the anisotropically conductive resin, and
the edge of the second main surface side of the semiconductor chip is covered with the resin located so as to cover the second main surface of the semiconductor chip.
(5) A magnetic disk apparatus comprises;
a disk-shaped magnetic recording medium that rotates in operation,
a magnetic head for writing the data in the magnetic recording medium and for reading out the data written in the magnetic recording medium,
a carriage mechanism having an arm on which the magnetic head is located and moving the magnetic head to an arbitrary position on the magnetic recording medium,
a wiring member having wiring,
a semiconductor chip having a first main surface and a second main surface that are opposed to each other and electrodes formed on the first main surface, the semiconductor chip being fixed to the wiring member in the state that the electrodes are facing to the wiring of the wiring member, and
a housing that contains the magnetic recording medium, the magnetic head, the carriage mechanism, the wiring member, and the semiconductor chip,
wherein;
the semiconductor chip is adhered and fixed to the wiring member with interposition of anisotropically conductive resin containing much conductive particles mixed in insulative resin base material,
the electrode of the semiconductor chip is electrically connected to the wiring of the wiring member with interposition of conductive particles contained in the anisotropically conductive resin,
the edge of the first main surface side of the semiconductor chip is covered with the anisotropically conductive resin, and
the edge of the second main surface side of the semiconductor chip is covered with the resin located so as to cover the second main surface of the semiconductor chip.
According to the above-mentioned means, in the case of the divided semiconductor chip formed by dicing, though many small debris and cracks are formed on the edge portion of the first main surface side and the edge portion of the second main surface side, the forming of debris and cracks from the edge portion of the first main surface side of the semiconductor chip and the edge portion of the back surface side is suppressed because the edge portion of the first main surface side of the semiconductor chip and the edge portion of the second main surface side are covered with the resins. As the result, the failure that the recording surface of the magnetic recording medium and the magnetic head are damaged and the failure in writing of the data and reading out of the data, both failures are caused from the debris interposed between the recording surface of the magnetic recording medium and a magnetic head, are prevented. In addition, the failure that the recording surface of the magnetic recording medium and the magnetic head are damaged and the failure in writing of the data and reading out of the data, both failures being caused by the fact that the magnetic recording medium rotates at high speed in a closed housing, air flow due to rotation of the magnetic recording medium blows off debris on the area other than that of the magnetic recording medium, and the debris falls down on the recording surface of the magnetic recording medium whereby the debris is interposed between the recording surface of the recording medium and a magnetic head, are suppressed. As the result, the reliability of the magnetic disk apparatus is improved.